CVE-2026-30871: Openwrt buffer overflow (CVSS 9.8)

Description

OpenWrt Project is a Linux operating system targeting embedded devices. In versions prior to 24.10.6 and 25.12.1, the mdns daemon has a Stack-based Buffer Overflow vulnerability in the parse_question function. The issue is triggered by PTR queries for reverse DNS domains (.in-addr.arpa and .ip6.arpa). DNS packets received on UDP port 5353 are expanded by dn_expand into an 8096-byte global buffer (name_buffer), which is then copied via an unbounded strcpy into a fixed 256-byte stack buffer when handling TYPE_PTR queries. The overflow is possible because dn_expand converts non-printable ASCII bytes (e.g., 0x01) into multi-character octal representations (e.g., \001), significantly inflating the expanded name beyond the stack buffer's capacity. A crafted DNS packet can exploit this expansion behavior to overflow the stack buffer, making the vulnerability reachable through normal multicast DNS packet processing. This issue has been fixed in versions 24.10.6 and 25.12.1.

CVSS 3.1 breakdown

Attack vectorNetwork

Attack complexityLow

Privileges requiredNone

User interactionNone

ScopeUnchanged

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

Openwrt≥ 25.12.0 < 25.12.1 · < 24.10.6

Remediation

Fixed in

Openwrt≥ 25.12.1

Patch & vendor advisories

https://github.com/openwrt/openwrt/security/advisories/GHSA-7c3j-f7w2-p8f6

References

https://github.com/openwrt/openwrt/releases/tag/v24.10.6Release Notes
https://github.com/openwrt/openwrt/releases/tag/v25.12.1Release Notes
https://github.com/openwrt/openwrt/security/advisories/GHSA-7c3j-f7w2-p8f6Vendor Advisory

Related CVEs

Recent high-severity vulnerabilities sharing a weakness type.

Frequently asked

Is CVE-2026-30871 being actively exploited?

CVE-2026-30871 is not in the CISA KEV catalog. Its EPSS exploit probability is 0.67%.

How severe is CVE-2026-30871?

CVE-2026-30871 has a CVSS 3.1 base score of 9.8, rated critical. EPSS estimates a 0.67% probability of exploitation.

Which products are affected by CVE-2026-30871?

Affected products include Openwrt.

How do I fix CVE-2026-30871?

Upgrade affected software to a fixed version, for example Openwrt 25.12.1 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

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